Benchmarking of ECCO calculations of LFR fuel assemblies by Monte Carlo calculations.

This thesis presents a preliminary analysis of the accuracy of ECCO deterministic calculations applied to LFR (Lead-cooled Fast Reactor) fuel assemblies, by comparing them with reference Monte Carlo simulations. The primary objective is to quantify and understand the discrepancies introduced by deterministic modeling when applied to fast reactor systems, particularly in view of ECCO's computational efficiency compared to Monte Carlo methods. Verification was carried out using the OpenMC Monte Carlo code, which is widely accepted as a reliable and validated tool in the nuclear community. Experimental data were not available at this stage, so the comparison is limited to numerical benchmarks. The deterministic calculations were performed using the ECCO module from the ERANOS 2.3 code system. The comparison focused on key neutronic parameters including the effective multiplication factor (k-eff), neutron flux distributions, reaction rates, and microscopic cross sections. The study modeled a representative LFR fuel assembly with hexagonal geometry, consistent with typical fast reactor core configurations. This code-to-code comparison effort highlights the strengths and weaknesses of ECCO for fast reactor applications and sets the groundwork for further studies. The absence of experimental data limits the scope of the conclusions, but future work will include sensitivity analyses and, where possible, comparisons against critical benchmark experiments to enhance the reliability of the validation process.